Document TAP_DEV_LONGSTACK/SHORTSTACK environs

Also, no need to exclude both the lib dir and the tap dir, since they're
the same thing.

Author: isaacs

bin/usage.txt

@@ -195,6 +195,18 @@ Environment Variables:
   TAP_BUFFER                  Set to '1' to run subtests in buffered
                               mode by default.
 
+  TAP_DEV_LONGSTACK           Set to '1' to include node-tap internals
+                              in stack traces.  By default, these are
+                              included only when the current working
+                              directory is the tap project itself.
+                              Note that node internals are always
+                              excluded.
+
+  TAP_DEV_SHORTSTACK          Set to '1' to exclude node-tap internals
+                              in stack traces, even if the current
+                              working directory is the tap project
+                              itself.
+
   _TAP_COVERAGE_              Reserved for internal use.
 
 Config Files:

lib/stack.js

@@ -8,10 +8,9 @@ var skip = process.cwd() !== tapDir ||
   +process.env.TAP_DEV_LONGSTACK !== 1
 ? [
     /node_modules[\/\\]tap[\/\\]/,
-    new RegExp(resc(tapDir)),
+    new RegExp(resc(tapDir) + '\\b', 'i'),
     new RegExp(resc(require.resolve('function-loop'))),
-    new RegExp(resc(path.dirname(require.resolve('bluebird/package.json')))),
-    new RegExp(resc(__dirname) + '\\b', 'i')
+    new RegExp(resc(path.dirname(require.resolve('bluebird/package.json'))))
   ]
 : []